Dam Alteration Identification by Extended Full-Waveform Inversion and Multiphase XFEM

水坝是水力发电、供水和防洪的重要建筑物。然而，今天运行中的大坝中有很大一部分超过50年的历史，因此其结构完整性的真实状况并不完全清楚。大坝的退化可能是由于短期影响(例如地震、冲击荷载等)和长期影响(例如老化、物理和化学风化、疲劳等)。虽然这些影响可能不会立即导致大坝坍塌/坍塌，但为了确保这些结构的最佳性能，有必要迅速确定可能危及大坝安全的区域。针对常规方法繁琐、费时、昂贵、效率低的问题，从全波反演法在地下勘探和岩土工程无损检测中的成功应用中得到启发。在这里，我们不仅打算利用FWI在提供精确和可靠结果方面的优势，而且还打算对具有明显多相-多场效应的结构的损伤识别方法进行适应和推广。为了增加所提出方法的稳健性和可靠性，将包括围绕结构运行的所有必要现象。此外，开发和应用一种新的两阶段方法将增加识别结果的稳定性(稳健性)和灵活性，该方法包括基于扩展有限元的反演和随后的FWI的组合。该方法具有通用性，甚至可应用于其他地震层析成像反问题。该技术还利用了计算技术的最新进展，在损伤识别中使用了交叉有限元、快速傅立叶变换、有限元-边界元混合方法和最优试验设计(DOE)。其目的是以非破坏性的方式高效、可靠地检测大坝中的异常，并将全波形反演(FWI)和常规结构健康监测技术在大坝中的应用所带来的复杂性和成本降至最低。

Dams are important structures employed in the generation of hydro-electricity, provision ofwater supply and for flood defense. However, a large percentage of dams in operation today are more than 50 years old and as such the true condition of its structural integrity is not fully known.The deterioration of dams may result both from short term effects (e.g earthquakes, impact loads, etc) and from long term effects (e.g. aging, physical and chemical weathering, fatigue etc). Though these effects may not lead to an immediate collapse/failure of the dam, it is necessary, in order to ensure optimum performance of these structures, to identify quickly regions which may jeopardize the safety of the dam. Unfortunately the conventional methods are tedious, time consuming, expensive and inefficient.The method proposed in this project draws inspiration from the recorded success of full-waveform inversion (FWI) application in subsurface exploration and for non-destructive testing (NDT) in geotechnical engineering. Here not only do we intend exploiting the advantages of FWI in providing precise and reliable results but also the adaptation and extension of the method for damage identification in structures with dominant multiphase-multifield effects. In order to increasethe robustness and reliability of the proposed method, all the necessary phenomena surrounding the operation of the structure will be incorporated. Additionally, the stability (robustness) and the flexibility of the identification results will be increased be developing and applying a novel two-stage approach which consists of a combination of an extended Finite Element (XFEM)-based inversion and a subsequent FWI. The approach is general and may be applied even to other inverse seismic tomography problems. The proposed technique also takes advantage of recent advancements in computing technology, works in damage identification using XFEM, FWI, FEM-BEM hybridmethods and the optimal design of experiments (DoE). The goal is to efficiently and reliably detect anomalies in dams in a non-destructive manner and to minimize the sophistication and cost incurred by the application of full-waveform inversion (FWI) and conventional structural health monitoring techniques in dams.